About 200 years ago, French physicist Augustin-Jean Fresnel is said to have developed thinner, lighter lenses for use in early 19th century lighthouses. We refer to these lenses today as Fresnel lenses. Since that time, Fresnel lenses have been used in a multitude of applications to provide focusing of light in a thinner and lighter form than could be provided by a bulk optical lens. It was also found that curved mirrors could be replaced by analogous thin, faceted constructions by making the facets reflective. Such mirrors are referred to as Fresnel mirrors.